#include<iostream>
#include<cmath>
#include<iomanip>
#define PI  3.141592653589793
using namespace std;
double distance(double Xa,double Ya,double Xb,double Yb);
int main()
{double x1,y1,x2,y2,x3,y3,x4,y4,p,a,b,c,d,circle; 
 while(cin>>x1>>y1>>x2>>y2>>x3>>y3)
   {
                                           
      a=distance(x1,y1,x2,y2);
      b=distance(x1,y1,x3,y3);
      c=distance(x2,y2,x3,y3);
      p=(a+b+c)/2; 
      d=(a*b*c)/(2*sqrt(p*(p-a)*(p-b)*(p-c)));
      circle=PI*d;
      cout<<setiosflags(ios::fixed)<<setprecision(2)<<circle<<endl;
      }
   system("pause");
   return 0;
      
}
 
 
double distance(double Xa,double Ya,double Xb,double Yb)
{double distance;
 distance=sqrt((Xa-Xb)*(Xa-Xb)+(Ya-Yb)*(Ya-Yb));
 return distance;
}
